US3299669A

US3299669A - Absorption refrigeration

Info

Publication number: US3299669A
Application number: US474834A
Authority: US
Inventors: Richard H Merrick
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 1965-07-26
Filing date: 1965-07-26
Publication date: 1967-01-24
Anticipated expiration: 1984-01-24

Description

Jan. 24, W67 R. H. MERRECK ABSORPTION REFRIGERATION Filed July 26, 1965 2 Sheets-Sheet 1 INVENTQR.

RICHARD H. MERRICK.

ATTQRNEY.

Jan. 24, 3967 R. H. MERRICK 3,299,669

ABSORPTION REFRIGERATION Filed July 26, 1965 2 Sheets-Sheet Z qpg.

, I I i I l 1 l J ATTORNEY.

United States Patent M 3,299,669 ABSORPTION REFRIGERATION Richard H. Merrick, Indianapolis, Ind., assignor to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware Filed July 26, 1965, Ser. No. 474,834 13 Claims. (Cl. 62-476) This invention relates to absorption refrigeration and more particularly to absorption refrigeration machines having refrigerant evaporators of the type which are adapted to cool air.

This invention will be described with reference to the preferred embodiment thereof wherein it is employed in conjunction with an absorption refrigeration system of the type using ammonia as a refrigerant and water as an absorbent. Because of the desirable temperaturepressure characteristics of such systems, it is common practice to use an ammonia-water system for air cooled absorption refrigeration machines.

Since ammonia vapor is toxic, it is necessary to assure that the ammonia refrigerant does not leak into the air being cooled during operation of the refrigeration machine. It has therefore been standard practice to provide a secondary chilled water circuit in conjunction with ammonia absorption machines. In such prior systems, the ammonia is evaporated in an evaporator coil to cool water which is passed thereover. The water is then pumped by means of :a chilled water pump to a secondary heat exchanger in a desired remote location. Air is passed over the secondary heat exchanger and is cooled by heat exchange with the chilled water. The chilled water is then returned through return conduits back to the evaporator where it is re-chilled by passing in heat exchange relation with the refrigerant in the evaporator coil. Should a leak occur in the evaporator coil due to corrosion or other damage, the ammonia will pass into the chilled water circuit, but will not leak into the air being cooled. The chilled water circuit is vented to the atmosphere so that ammonia leaking into it can escape to a location where it will not cause injury to occupants of the conditioned space.

Prior systems of the type described require a secondary chilled water pump, a secondary refrigerant heat exchanger :and secondary refrigerant piping to connect the secondary heat exchanger to the evaporator coil. These components materially add to the cost of refrigeration systems of the type described. It would be desirable to achieve the safety of a vented secondary chilled water system, but at the same time, to eliminate the cost and complexity of the secondary heat exchanger, secondary chilled water pump, and their associated piping.

It is a principal object of this invention to provide an improved absorption refrigeration system for cooling air which is adapted to employ :a toxic refrigerant without danger of refrigerant leakage into the air being cooled.

It is a furtherv object of this invention to provide an improved refrigeration system of a type having an evaporator which is adapted to employ a toxic refrigerant without danger of refrigerant leakage into the space being refrigerated.

In accordance with a preferred embodiment of this invention there is provided an improved evaporator construction for an absorption refrigeration machine of the type employing amomnia as a refrigerant and water as an absorbent. The evaporator may comprise a pair of tube sheets having a plurality of heat exchange tubes disposed therebetween for heat exchange with the air being cooled. Evaporator tubes are disposed within the heat exchange tubes and are connected between the condenser and absorber of the absorption refrigeration Patented Jan. 24, 1967 machine. A suitable displaceable liquid medium such as water is disposed between the evaporator tubes and the interior of the heat exchange tubes. Liquid filled headers are disposed about the tube sheets so that the evaporator coil is submerged in the liquid medium. At least one of the headers is vented to the atmosphere or some other suitable location. Preferably, a layer of oil or other relatively non-volatile fluid may overlie the surface of the liquid medium in the vented header to prevent loss of the liquid by evaporation, if the liquid medium is one which is readily volatilized in use.

The liquid medium is disposed in :a thin layer between the heat exchange tubes and the evaporator tubes. The thin layer of liquid provided relatively good heat conduction between the evaporator tubes and the heat exchange tubes. At the same time, the liquid medium is displaceable and serves as a path for the escape of refrigerant in the event that a defect should occur in the wall of the evaporator tubes of a nature which permits refrigerant to escape through the wall of the evaporator tubes. In that event, the escaping refrigerant will pass through the liquid medium between the evaporator and heat exchange tubes, and through the tube headers to the atmosphere or other location to which they are vented. Thus, escape of refrigerant into the stream of air being cooled is prevented. Furthermore, the use of water as the liquid medium surrounding the evaporator tubes and in the headers has the additional advantage of serving as an absorbent medium to absorb escaping refrigerant. The liquid medium surrounding the evaporator tubes may also contain a suitable corrosion inhibitor to reduce the likelihood of failure of evaporator tubes and to help prevent leakage of refrigerant.

The evaporator of the absorption refrigeration machine may be located so that the headers are in heat exchange relation with ambient atmosphere to prevent evaporation of the liquid medium during the heating season and to prevent excessive condensation of moisture from the air into the headers during the cooling season. The evaporator may be located in a housing containing the other components of the absorption refrigeration machine. However, the improved evaporator construction may be disposed instead within an air duct in the interior of the building being conditioned and the refrigerant liquid and vapor conduits extending between the evaporator and an externally located absorption refrigeration machine, may be shrouded by a conduit which is vented to the atmosphere.

These and other objects of this invention will become more readily apparent by reference to the following specification and attached drawings wherein: '1 A FIGURE 1 is a schematic diagram partly in cross section illustrating an obsorption refrigeration machine embodying one application of this invention; and

FIGURE 2 is a perspective view partly in cross section illustrating 'a slightly modified application of this invention.

Referring particularly to the drawing, there is shown an absorption refrigeration system having an absorber 10, a

condenser 11, an evaporator 12, and a generator 13 connected to provide refrigeration. A pump 14 is employed to circulate weak absorbent solution from absorber 10 to generator 13. As used herein, the term weak absorbent solution refers to a solution which is weak in absorbing power, and the term strong absorbent solution refers to a solution which is strong in absorbing powder. A suitable absorbent solution for use in the system described is water, and a suitable refrigerant is ammonia. For convenience, the absorbent liquid will be referred to as an absorbent solution although it will be appreciated that pure water is not technically a solution.

Liquid refrigerant is passed from condenser 11 through liquid line 23, refrigerant restriction 24, the exterior passage of liquid suction heat exchanger .25, second rcfrigerant restriction 26, and refrigerant line 19 to evaporator tubes or coil 27 of evaporator 12. Heat from the air or other fluid to be chilled, passing over the evaporator, is given up to the refrigerant which vaporizes in the interior passage of the evaporator. The refrigerant vapor passes from tubes or coil 27 through vapor line 28, the interior passage of liquid suction heat exchanger 25, to mixing line 29 where it is mixed with strong solution returning to the absorber from the generator.

The mixture of refrigerant vapor and strong solution passes through mixing line 29 into the heat exchange tubes or coil which forms absorber 10. Air is passed over the exterior of the absorber coil by fan 15 to cool absorbent solution therein and increase its absorbing power. The absorbent solution is weakened as it absorbs refrigerant vapor during its passage through the absorber. By the time the absorbent solution reaches the discharge end of the absorber coil, the refrigerant vapor is completely absorbed in the absorbent solution and the solution has become weak in absorbing power by the absorption of the vapor.

The weak absorbent solution passes through weak solution line 30 to a purge tank 31 where noncondensible gases are collected and withdrawn from the system. The weak solution is then forwarded by solution pump 14 through weak solution line 32 to combined rectifier and heat exchanger section 35.

Rectifier and heat exchanger section 35 comprises an outer shell 46 forming a vapor passage. Shell 46 contains an inner heat exchange coil 45 and a concentric outer heat exchange coil 36, as shown in the drawing. Preferably outer heat exchange coil 36 is spirally disposed along the inner wall of shell 46 and it may be provided with suitable fins for enhancing heat transfer.

Coils

36 and 45 form a solution heat exchanger between the entire quantity of relatively hot strong solution passing from the generator to the absorber and the entire quantity of relatively cool Weak solution passing from the absorber to the generator. The amount of heat transfer surface provided between the strong and weak solution is designed so that the weak solution is brought to just about its boiling point so that vapor is not formed in the solution heat exchanger.

The weak solution from line 32 passes through coil 36 in the annular space between inner heat exchange coil 45 and outer heat exchanger coil 36 where the weak solution is heated to substantially its boiling point by heat exchange with strong solution. After passing through coil 36, the heated weak solution is discharged from opening 37 onto one of a plurality of bafiles or plates 39 in analyzer column 38.

Analyzer 38 comprises a tubular member having a plurality of plates 39 which provide surfaces for contact of vapor with the reflux and the solution which wets the surfaces of the plates. The weak solution passes successively over the plurality of plates and is discharged from the bottom of the analyzer into a generator reservoir 40. Generator reservoir 40 provides solution storage for part load operation conditions and allows for solution and refrigerant charging tolerance, and compensates for manufacturing variations in machine volume.

Weak solution from generator reservoir 40 passes through line 49 into generator coil 50. The solution in coil 50 is heated by suitable means such as gas burner 51 causing the solution to boil thereby forming vapor. The vapor and hot solution is discharged from coil 50 into separation chamber 53, formed by a baffle or weir 52, where the vapor separates from the remaining strong solution. Preferably, some of the solution normally spills over the top of baffle 52 and is recirculated through line 49 to generator coil 50. It will be understood that the solution in separation chamber 53 has been concentrated by vaporizing refrigerant therefrom in generator 13.

Vapor formed in generator 13 passes concurrently with strong solution through the vapor passage 55 formed in the upper portion of genertaor reservoir 40, through analyzer 38 and through the vapor passage formed by shell 46 of rectifier 35 to condenser 11.

The concentrated or strong absorbent solution from separation region 53 is at the relatively high generator pressure and passes through heat exchange coil 48 in generator reservoir 40, heat exchange coil 47 in the analyzer column, and inner :heat exchange coil 45 in the rectifier. The strong solution then passes through line 60 and restriction 61 into mixing line 29 and absorber 10 on the relatively low pressure side of the system.

Heat from the strong solution passing through coil 48 boils the weak solution in the generator reservoir to vaporize refrigerant therefrom. The heat exchange which takes place in the generator reservoir results in cooling the strong solution flowing through coil 48 so that it enters the analyzer and rectifier respectively at the best temperature to achieve maximum efficiency with minimum heat trans fer surface.

A portion of coil 48 is submerged below the level of weak solution in reservoir 40 and another portion of the coil is disposed in the vapor passage above the weak solution. The boiling of the weak solution causes the portion of coil 48 which is disposed in vapor passage 55 to be wetted with solution. As the strong solution passes through coil 48, it becomes progressively cooler. Vapor formed in the generator and in the reservoir passes through the vapor passage 55 and contacts the exposed and wetted portion of coil 48 in reservoir 40, and mass and heat transfer takes place with the weak solution boiling in the reservoir. It will be appreciated that ammonia vapor will be boiled from the weak solution in the reservoir and that water vapor will be condensed from the vapor space into the weak solution in proportions resulting in an enrichment of the refrigerant content of the vapor passing through the reservoir. Also the condensation of water vapor into the weak solution will liberate additional heat which assists in vaporizing the solution.

Similarly, as the vapor passes from the reservoir upwardly through analyzer column 38, a mass and heat transfer takes place 'between the weak solution passing downwardly over plates 39 in the columns and further enriches the refrigerant content of the vapor.

The vapor then passes through rectifier 35 Where it is placed in heat exchange relation with the weak solution passing through coil 36. The heat transfer which takes place in the rectifier results in condensing additional water from the vapor which then leaves the rectifier in a highly purified or enriched state.

The purified refrigerant vapor passes from rectifier 35 through line 58 into the coil of condenser 11. Fan 15 passes air over condenser 11 causing the refrigerant vapor to condense. The condensed refrigerant passes through line 23 and restriction 24 into evaporator 12, as previously explained.

As the vapor passes through rectifier 35, the reflux or solution which is condensed, flows by gravity to analyzer 38 and passes downwardly through the analyzer column along with weak solution discharged from outlet 37 of coil 36. This rectifier condensate is heated along with weak solution in the analyzer to produce additional vapor by heat exchange with strong solution passing through coil 47,

In accordance with the embodiment of this invention illustrated in FIGURE 1, evaporator 12 includes a pair of spaced tube sheets 71 and 72. disposed therein. A plurality of hollow, parallel, heat exchange tubes 75, having open ends, are disposed between headers 71 and 72 and are secured in fluid tight engagement therewith. The evaporator also includes a plurality of hollow tubular parallel evaporator tubes 20 disposed concentrically within heat exchange tubes 75. Return hends 76 are provided at the ends of evaporator tubes 20 to form an evaporator coil. Helical or longitudinal fins or other spacing means (not shown) may be provided on the exterior of evaporator tubes 20 or on the interior of heat exchange tubes 75, or on both tubes, if desired. Preferably, heat exchange tubes 75 are provided with exterior plate -fins 77 or other extended heat transfer means for contact with air to be cooled.

A refrigerant liquid line 19 extends between restriction 26 and the first evaporator tube 20 of the evaporator coil. A refrigerant vapor line 28 extends from the last evaporator tube 20 of the evaporator coil to absorber 10.

Headers

73 and 74 are connected in fluid tight engagement with tube sheets 71 and 72 respectively, and enclose return bends 76 and the open ends of heat exchange tubes 75. A liquid medium 82, such as water, fills

headers

73 and 74 to level 82 which is above the uppermost one of heat exchange tubes 75. A layer of relatively lighter, less volatile, and immiscible liquid 83, such as oil, overlies the surface of the liquid 82 in theevent the liquid is one which is readly vaporized during operation of the system. The oil, or other liquid, inhibits evaporation of the heat exchange liquid medium from

headers

73 and 74. Liquid 82 may comprise any displaceable or fiowable medium such as slurries or gels, and may include powdered metal for enhanced thermal conductivity.

Headers

73 and 74 may have a small vapor space at the upper portion thereof. The upper portions of at least one of the headers is vented to the atmosphere or other suitable location by vent passages 80 and 81 respectively.

Evaporator 12 in the embodiment shown in FIGURE 1 may be disposed in a housing (not shown) containing the other components of the absorption refrigeration machine and the housing may be located exteriorly of the building or other space being conditioned. Suitable duct or passage means is provided to admit either room air or outside air into the region about heat exchange tubes 75 and fins 77. This air is passed over the heat exchange tubes 75 where it is cooled 'by heat exchange with the refrigerant evaporating inside evaporator tubes 20, The cooled air is then passed through duct 78 into the building or other desired location.

In the event of leakage of refrigerant from the evaporator coil, such as might be occasioned by corrosion of evaporator tubes 20, the leaking refrigerant will displace the liquid and pass through the space between evaporator tubes 20 and heat exchange tubes 75 into one or the other of

headers

73 and 74. The refrigerant vapor will then pass upwardly through the liquid medium in the header and through the layer of oil or other non-volatile liquid into vent passages 80 or 81, from which it is exhausted into the atmosphere.

In the event of a refrigerant leakage from the evaporator tubes, due to corrosion of the tubes, the leaking refrigerant will displace the liquid and p ass between evaporator tubes 20 and heat exchange tubes 75 and into one or the other of

headers

73 and 74. The refrigerant cannot leak into the stream of air passing over heat exchange tubes 75 and therefore will not contaminate the stream of air being cooled. Even if the heat exchange tubes and the evaporator tubes nearly touch each other, the thin film of liquid medium between them will provide 'a path of relatively low resistance to'the passage of leaking refrigerant vapor to the atmosphere or other desired location.

I It is desirable that the film of liquid medium between the heat exchange tubes and the evaporator tubes be relatively'thin inorder to enhance the heattransfer through the liquid medium which serves as a liquid heat transfer medium. Because the heat exchange tubes and the evaporator tubes are not in tight engagement with each other, the likelihood of a corrosion path through an evaporator tube also extending its way through a heat exchange tube is negligible.

The liquid medium 82 between heat exchange tubes 75 and evaporator tubes 20 may comprise an absorbent medium such as water to further lessen the likelihood of passage of refrigerant into the air stream being cooled. Thus, ammonia vapor leaking into the water between the evaporator tubes and heat exchange tubes will be absorbed in the water and any portion of the ammonia which is not absorbed in the water will be exhausted into the atmosphere or other desired location through vent 80. It is preferred and convenient to provide a suitable corrosion inhibitor in the liquid medium, to lessen the corrosion of both the evaporator tubes and the heat exchange tubes. For example, sodium chromate may be suitably employed as an inhibitor where water is the liquid medium. It will be seen that corrosion of either the evaporator tubes 20 or return bends 76 will not result in contamination of the air being cooled by the refrigerant by the practice of this invention. Alternatively, an oil such as engine oil may be used as the liquid medium. Engine oil is a suitable and a desirable liquid medium because of its relatively low volatility and its high stability; also, it normally has corrosion inhibitors dissolved in it which prevent corrosion of the metal tubes.

In the above described embodiment of this invention, evaporator 12 is located outside of the building being conditioned, and the cooled air is supplied to the building through duct 78. Preferably,

headers

73 and 74 are disposed in heat exchange relation with the ambient atmosphere. By this means, the heat exchange fluid in the headers is cooled when the ambient air is cold to thereby inhibit evaporation of the heat exchange liquid during the heatingseason. On the other hand, when the ambient air is warm, such as during the cooling season, the tendency of moisture from the air to condense in vent passages 81, due to heat exchange with the cold evaporator, is reduced.

A modified embodiment of this invention is illustrated in FIGURE 2. In this embodiment most of the components of the absorption refrigeration machine are located exteriorly of the conditioned space in a suitable housing 90. Housing has a grill 91 for admitting ambient air, and a fan grill 92 for exhausting the ambient :air from the housing. Evaporator 12 is connected by

conduits

19 and 28 to the remainder of absorption machine in housing 90. Preferably

conduits

19 and 28 are disposed adjacent and in heat exchange relation with each other to form a liquid suction heat exchanger 125. Evaporator 12 is located inside the building or other space to be conditioned in the warm air duct connecting furnace 93 with air distribution duct 78.

Suitable joint means and valves 111, 112 may be provided to connect

lines

19 and 28 with evaporator 12 and with the other components of the absorption refrigeration machine. Evaporator 12 in this embodiment is similar to the evaporator previously described except that an additional outer vent tube or passage 96 is provided about and spaced from refrigerant lines,19. and 28 to receive any refrigerant which mayleak from either

lines

19 or 28. Vent passage 96 is secured, adjacentv one end 98 thereof, in sealing relation with housing 70 ofevaporator '12. Vent passage 96 extends from evaporator 12 through wall 99 ofthe buildingor space being cooled tothe outside or to some other suitable location at which it is safe to vent refrigerant vapor. End 97 of vent passage 96 is preferably open to the atmosphere. Consequently, refrigerant leaking from either lines .19 or 28 is vented to the outside of the space being cooled and the refrigerant cannot contaminate the conditioned area.

Vent passages 80 and 81 extending from header 73 are connected to vent line 94 which may either extend directly through wall 99 or may terminate in outer tube 96 as shown in the drawing. As in the preceding embodiment, any refrigerant leaking from the evaporator coil 27 passes through the liquid heat exchange medium disposed sponsor;

7 in the space between evaporator tubes 20 and heat exchange tubes 75 into passages 80 and 81, from which the refrigerant vapor is exhausted to the atmosphere so that the air being cooled is not contaminated.

Various modifications of this invention may be envisioned within the scope thereof. For example, evaporator 12 may be employed in communication with any refrigeration system wherein it is desired to prevent the cooling medium from escaping and contaminating the cooled space. Consequently, evaporator 12 is suitable for use with refrigeration systems employing such toxic refrigerants as sulfur dioxide and menthol chloride. Furthermore, the evaporator may be disposed in any desired location because the danger of contamination of the conditioned air is minimized. A lso, evaporator 12 may assume other configurations such as a continuous concentric serpentine coil having a vented, liquid filled, header on at least one end of the outer tube thereof. While water has been described as being a desirable liquid medium with which to fill the space between the evaporator tubes and the heat exchange tubes, it will be appreciated that other media such as mineral oil or engine oil may be satisfactory for this purpose. In a similar manner fluids other than air may be cooled by an evaporator of the type described.

It will be seen that by the use of this invention, the necessity of secondary chilled Water pump and a separate secondary refrigerant heat exchange coil is eliminated so that the cost and complexity of a refrigeration system employing this invention is reduced. Furthermore, the invention is effective to prevent contamination of the cooled space irrespective of the nature of the refrigerant employed and makes it possible to employ toxic refrigerants with safety.

While preferred embodiments of this invention have been described for purposes of illustration, it will 'be appreciated that the invention may be otherwise embodied within the scope of the following claims.

I claim:

'1. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(B) a generator for concentrating weak absorbent solution and forming vapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator; and

(D) an evaporator for evaporating a refrigerant to provide cooling, said evaporator comprising:

' (1) an evaporator passage including an evaporator tube connected to receive liquid refrigerant from said condenser and to discharge vaporized refrigerant to said absorber;

(2) a heat exchange tube enclosing at least a portion of said evaporator tube;

(3) a liquid medium filling the region between said evaporator tube and said heat exchange tube; and

(4) a passage means for passing any refrigerant leaking from said evaporator tube into said liquid medium to a desired location.

2. An a'bsonption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(C) a condenser for condensing refrigerant vaporized in said generator; and

(1) an evaporator passage including an evaporator tube connected to receive liquid refrigerant from said condenser and to discharge vaporized refrigerant to said absorber;

(2) a heat exchange tube enclosing at least a portion of said evaporator tube;

(3) an absorbent .liquid medium capable of ab:- sorbing refrigerant disposed between said evaporator tube and said heat exchange tube; and

(4) passage means for passing any refrigerant leaking from said evaporator tube into said liquid medium to a desired location.

3. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(C) a condenser for condensing refrigerant vaporized in said generator; and

(2) a heat exchange tube enclosing at least a portion of said evaporator tube;

(3) a volume of water filling the region between said evaporator tube and said heat exchange tube; and

(4) passage means for passing any refrigerant leaking from said evaporator tube into said water to a desired location.

4. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(C) a condenser for condensing refrigerant vaporized in said generator; and

(2) a heat exchange tube enclosing at least a portion of said evaporator tube;

(3) a liquid medium filling the region between said evaporator tube and said heat exchange tube;

(4) a corrosion inhibitor dissolved in said liquid medium to inhibit corrosion of said evaporator tube; and

(5) passage means for passing any refrigerant leaking from said evaporator tube into said liquid medium to a desired location.

5. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

('B) a generator for concentrating weak absorbent solution and forming vapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator; and

(D) an evaporator for evaporating a refrigerant to provide cooling,said evaporator comprising:

( 1) an evaporator passage including an evaporator tube connected to receive liquid refrigerant from said condenser and to discharge vaporized refrigerant to said absorber,

(1) a heat exchange tube enclosing at least a portion of said evaporator tube, said heat exchange tube being spaced from said evaporator tube,

(3) a fluid medium disposed in and substantially filling the space between said evaporator tube and said heat exchange tube,

(4) passage means for passing any-refrigerant leaking into said space between said evaporatortube and said heat exchange tube to a desired location,- and (5) means to pass air to be cooled over the ex terior surface of said heat exchange tube so that said air passes in heat exchange relation with refrigerant in said evaporator tube, said air being cooled being separated from said refrigerant by the space between said evaporator tube and said heat exchangetube to prevent contamination of said air in the event of refrigerant leaking through said evaporatortu'be. 6. An absorption refrigeration system comprising: (A) an absorber for absorbing refrigerant vapor; (B) a generator for concentrating weak absorbent solution and forming vapor therefrom; (C) a condenser for condensing refrigerant vaporized in said generator; and (D) an evaporator for evaporating a refrigerant to provide cooling, said evaporator comprising:

(1) a plurality of parallel open ended, heat exchange tubes adapted to be disposed in a location to have air passed over the exterior surfaces of said heat exchange tubes to cool said air,

(2) an evaporator tube disposed within each of said heat exchange tubes, said evaporator tubes being connected together by passage means to form an evaporator passage,

(3) a liquid medium substantially filling the space between said evaporator tubes and said heat exchange tubes; and

(4) passage means placing said space filled with said liquid medium in communication with a desired location for exhausting any refrigerant vapor leaking into said space to said desired location to effectively prevent contamination of the air being cooled with refrigerant by venting any refrigerant leaking through said evaporator passage to said desired region through said liquid filled space. 7. An absorption refrigeration system comprising: (A) an absorber forabsorbing refrigerant vapor; (B) a generator for concentrating weak absorbent solution and forming vapor therefrom; (C) a condenser for condensing refrigerant vaporized in said generator; and (D) an evaporator for evaporating a refrigerant to provide cooling, said evaporator comprising:

(1) a heat exchanger including a heat exchange tube having an open end,

(2) an evaporator tube disposed within said heat exchange tube, said evaporator tube being connected to receive refrigerant from said condenser and to discharge vapor formed therein to said (3) liquid header means disposed about said open end of said heat exchange tube,

(4) a liquid medium disposed in said liquid header means, said liquid medium filling said header means to a level above said heat exchange tube, and

(5) means to vent said liquid header to a desired location to pass any refrigerant which leaks from said evaporator tube to said desired location through said liquid medium and to prevent leakage of said refrigerant into air passing over said heat exchange tube.

8. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(C) a condenser for condensing refrigerant vaporized in said generator; and

( 1) a heat exchanger including a heat exchange tube having an open end,

(2) an evaporator tube disposed within said heat exchange tube, said evaporator tube being connected to receive refrigerant from said con-' denser and to discharge vapor formed therein to said absorber,

(3) liquid header means disposed about said open end of said heat exchange tube,

- (4) a liquid medium disposed in said liquid header means, said liquid medium filling said header means to a level above said heat exchange tube,

(5) means to vent said liquid header to a desired location to pass any refrigerant which leaks from said evaporator tube to said desired location through said liquid medium and to prevent leakage of said refrigerant into air passing over said heat exchange tube, and

(6) a layer of a relatively less volatile and relatively lighter liquid overlying the surface of said liquid medium to inhibit evaporation thereof.

9. An absorption refrigeration system comprising:

(A) an absonberfor absorbing refrigerant vapor;

(C) a condenser for condensing refrigerant vaporized in said generator; and

(D) an evaporator for evaporating a refrigerant to provide c'oolin-g, said evaporator comprising:

(1) a plurality of heat exchange tubes disposed in parallel relation to each other, said heat exchange tubes having open e-nds, and being adapted to have air passed over their exterior surface for cooling said air,

(2) a pair of liquid headers disposed about the open ends of each of said heat exchange tubes at both ends thereof,

(3) an evaporator tube disposed within said heat exchange tubes, said evaporator tube being connected to receive refrigerant from said condenser and to discharge refrigerant vapor formed therein to said absorber,

(4) a liquid heat'exchange medium disposed between said evaporator tube and said heat exchange tubes, and in said headers, and

(5) passage means for passing refrigerant from said headers to a desired location so as to prevent passage of refrigerant from said evaporator tube into the air being cooled in the event of a leak in said evaporator tube.

10.- An absorption refrigeration. system employing ammonia as a refrigerant and comprising:

, (A) an absorber for absorbing refrigerant vapor;

(C) a condenser for condensing refrigerant vaporized in said generator; and

(D) an evaporator for evaporating a' refrigerant to provide cooling, said evaporator comprising:

(1) a pair of spaced, tube-sheets,

(2) a plurality of open ended heat exchange tubes extending through said tube sheets to form a heat exchanger,

(3) a header enclosing the open ends of said heat exchange tubes at each of said tube sheets, said header forming a chamber adapted to hold a liquid, and both of said headers having an upper region in communication with the atmosphere for venting :gas from said header to said ambient atmosphere, said headers being exposed to the ambient atmosphere for heat exchange therewith,

(4) an evaporator passage comprising an evaporator tube disposed within and in spaced relation with each of said heat exchange tubes, said evaporator tubes being connected together by return passages to form an evaporator coil, said return passages being disposed within said headers, said evaporator coil being connected to receive liquid ammonia from said condenser and to discharge ammonia vapor formed therein to said absorber,

() Water substantially filling said headers to a level above said heat exchange tubes and the spaces between said heat exchange tubes and said evaporator tubes, and

(6) a layer of oil covering the surface of said Water in the upper regions of said headers to inhibit evaporation of water from said headers into the ambient air.

11. An absonpton refrigeration system comprising: a

(A) an absorber for absorbing refrigerant vapor;

(C) a condenser for condensing refrigerant vaporized in said generator; and I (D) an evaporator for evaporating a refrigerant to provide cooling, said evaporator comprising:

-(1) an evaporator passage including an evaporator tube connected to receive liquid refrigerant from said condenser and to discharge vaporized refrigerant to said absorber,

(2) a heat exchange tube enclosing at least a portion of said evaporator tube,

(3) a liquid medium disposed between said evaporator tube and said heat exchange tube,

(4) passage means for passing any refrigerant leaking from said evaporator tube into said liquid medium to a desired location; and

(5 a layer of a relatively lighter and less volatile liquid covering the surface of said liquid medium to inhibit evaporation thereof.

12. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(C) a condenser for condensing refrigerant vaporized in said generator; and

(1) an evaporator passage, said evaporator passage being connected by a refrigerant liquid passage to receive liquid refrigerant from said condenser, and being connected by a refrigerant vapor passage to discharge refrigerant vapor to said absorber,

(2) means to pass air to be cooled "in heat exchange relation with said evaporator,

(3) said refrigerant liquid and refrigerant vapor passages being enclosed in an outer tube extending from said evaporator, said outer tube being spaced from said refrigerant passages, and

(4) passage means to vent the space between said outer tube and said refrigerant passages to a desired location to effectively prevent contamination of air being cooled by said evaporator with refrigerant in the event of leakage thereof from one of said passages by passing said refrigerant through the space between said outer tube and said refrigerant passage to said desired location. 13. An absorption refrigeration system comprising: (A) an absorber for absorbing refrigerant vapor; (B) a generator for concentrating weak absorbent solution and forming vapor therefrom; (C) a condenser for condensing refrigerant vaporized in said generator; and (D) an evaporator for evaporating a refrigerant to provide cooling, said evaporator comprising:

(1) an evaporator passage disposed at a location remote from said absorber, condenser and generator, said evaporator passage being connected by a refrigerant liquid passage to receive liquid refrigerant from said condenser, and being connected by a refrigerant vapor passage to discharge refrigerant vapor to said absorber,

(2) means to pass air to be cooled in heat exchange relation with said evaporator,

(3) said refrigerant vapor passage and said refrigerant liquid passage being disposed in heat exchange relation with each other,

(4) said refrigerant passages being enclosed in an outer tube extending from said evaporator, said outer tube being spaced from the outermost of said refrigerant passages, and

(5) passage means to vent the space between said outer tube and said refrigerant passages to a desired location to effectively prevent contamination of air being cooled by said evaporator with refrigerant in the event of leakage thereof from one of said passages by passing said refrigerant through the space between said outer tube and said refrigerant passage to said desired location.

References Cited by the Examiner Rhodes 62399 X LLOYD L. KING, Primary Examiner.

Claims

1. AN ABSORPTION REFRIGERATION SYSTEM COMPRISING: (A) AN ABSORBER FOR ABSORBING REFRIGERANT VAPOR; (B) A GENERATOR FOR CONCENTRATING WEAK ABSORBENT SOLUTION AND FORMING VAPOR THEREFROM; (C) A CONDENSER FOR CONDENSING REFRIGERANT VAPORIZED IN SAID GENERATOR; AND (D) AN EVAPORATOR FOR EVAPORATING A REFRIGERANT TO PROVIDE COOLING, SAID EVAPORATOR COMPRISING: (1) AN EVAPORATOR PASSAGE INCLUDING AN EVAPORATOR TUBE CONNECTED TO RECEIVE LIQUID REFRIGERANT FROM SAID CONDENSER AND TO DISCHARGE VAPORIZED REFRIGERANT TO SAID ABSORBER; (2) A HEAT EXCHANGE TUBE ENCLOSING AT LEAST A PORTION OF SAID EVAPORATOR TUBE; (3) A LIQUID MEDIUM FILLING THE REGION BETWEEN SAID EVAPORATOR TUBE AND SAID HEAT EXCHANGE TUBE; AND (4) A PASSAGE MEANS FOR PASSING ANY REFRIGERANT LEAKING FROM SAID EVAPORATOR TUBE INTO SAID LIQUID MEDIUM TO A DESIRED LOCATION.